Gather your supplies:
• Propeller 40 x 11 x 200mm pine
• Shaft 8mm-dia. x 250mm hardwood dowel
• Pull handle 8mm-dia. x 80mm hardwood dowel
• Launcher 25 x 350mm plastic rigid conduit
You’ll also need:
Clamps; pencil; set square; drill and drill bits; 40- and 120-grit sandpaper; sanding block; belt sander (optional); 3mm-dia. round shoelace; wood glue
Find centre of propeller and measure 10mm to each side. Square lines across propeller at these marks. Repeat on other side.
Finger gauge along timber about 2mm from leading and back edge on both sides. To do this, hold pencil on edge to be marked, 2mm from edge, then run along edge using finger as a guide so it draws a line parallel to edge – 2mm line should be on opposite sides of edges, each side of centre of propeller.
Draw a diagonal across edge at each end to join up finger gauged lines. They should run opposite direction at each end. The idea is to shape the blade so each side slopes in different directions.
To shape propeller, you could use a chisel to remove bulk of pine or just sand using a block after clamping to a sturdy surface. Doing it by hand with 40-grit paper and a block is effective (less chance of mistakes) but slow. It’s much easier to use a belt or orbital sander as we have.
Do not use too much pressure with sander. It will also give flatter propeller surfaces.
Turn propeller over to shape other side but be gentle as it will be getting to about 2mm thick. It’s best supported by bench. The roll at front of a belt sander gives a natural curve to the flat centre section of rotor.
To work on other end of propeller, clamp small amount of flat section to bench. Work gently as material is getting thin. Keep sanding until it is the right shape.
Switch to 120-grit sandpaper to smooth and refine propeller, sanding by hand. Check blades look same in shape and bulk on each side of centre.
Drill an 8mm hole in exact centre of propeller, then glue dowel shaft in place in hole.
Drill a 3mm hole through shaft, 200mm down from propeller. This needs to be large enough so aglet on 3mm- dia. round shoelace can easily slip in and out. Also drill a similar hole in centre of pull handle.
Measure 200mm down from top of launcher, and drill a 13mm hole through both sides of tube. Clean up using sandpaper.
Tie shoelace to pull handle, then place propeller assembly into launcher. Align shaft and launcher holes, inser t aglet of shoelace into hole in shaft, then wind propeller in a clockwise direction so shoelace feeds neatly down shaft. Hold launcher so propeller is above eye level, then pull on string so it comes right out of shaft. How hard you pull lace determines height and length of flight. The direction, well that’s another matter. Be prepared to chase it.